WASHINGTON — When the Islamic State stormed onto the scene in Syria and Iraq, it seemed focused on seizing territory in its own neighborhood. But in the last two weeks, the so-called soldiers of the caliphate appear to have demonstrated a chilling reach, with terrorist attacks against Russia, in Lebanon and now inFrance.

The seemingly synchronized assaults that turned Paris into a war zone on Friday came just days after a bombing targeted a Shiite district of Beirut controlled by Iran’s ally, Hezbollah, and a Russian passenger jet was downed over Egypt.The rapid succession of strikes, all claimed by the Islamic State, suggested that the regional war has turned into a global one.

For President Obama and American allies, the attacks are almost certain to force a reassessment of the threat and may prompt a more aggressive strategy against the Islamic State, known variously asISIS, ISIL or Daesh. Mr. Obama met with national security aides Saturday before his scheduled departure for Antalya, Turkey, where he was to consult with other world leaders in a Group of 20 summit meeting now sure to be dominated by discussion of the Paris attacks.

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“ISIS is absolutely a threat beyond the region,” said Frances Fragos Townsend, the top White House counterterrorism adviser under President George W. Bush. “We must not continue to assume that ISIS is merely an away threat. It clearly has international ambitions beyond its self-proclaimed caliphate.”

The situation was already complex enough, with varied players with separate interests involved in the war.

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Iran is fighting the Islamic State, but is hardly an ally of the United States. Russia says it is fighting the Islamic State as well, but mainly seems to be trying to bolster the government of President Bashar al-Assad, who Mr. Obama has said must step down.

To an extent, the United States had viewed the Islamic State as a regional problem to fence in; indeed, just the day before the Paris attacks, Mr. Obama told ABC News that “we have contained them” in Iraq and Syria. But now the debate will be transformed and Mr. Obama may have to rethink the contours of the war he has been waging.

Obama on the Paris Attacks

“Truthfully, I can’t imagine how it doesn’t change their approach,” saidMichael E. Leiter, who was the director of the National Counterterrorism Center under Mr. Bush and Mr. Obama. “When you give this kind of organization this much freedom of movement and go after it this incrementally, people shouldn’t be surprised by things like the aircraft bombing.”

Matthew G. Olsen, another former director of the counterterrorism center, said the series of major attacks would compel the White House to take additional steps. “All of this raises the stakes for the U.S. and increases pressure on the U.S. and the West to respond more aggressively,” he said.

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Escalating action against the Islamic State carries its own risks. The Russian airliner was attacked after Moscow intervened in Syria. And the Islamic State has warned it would step up strikes against those countries that have joined the American-led coalition fighting the group in Iraq and Syria.

“The operational tempo is increasing on both sides,” Mr. Olsen said. “We’re increasing our attacks in Syria and Iraq, and ISIS is increasing their attacks as well.”

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Police officers outside the Bataclan music hall, which was a scene of carnage on Friday night.CreditPierre Terdjman for The New York Times

Representative Adam B. Schiff of California, the ranking Democrat on the Intelligence Committee, said the attacks should dispel any illusions about the nature of the Islamic State. “It will add another sense of urgency to defeating” it, he said, “and that will be very hard to do without eliminating its sanctuary. If this doesn’t create in the world a fierce determination to rid ourselves of this scourge, I don’t know what will.”

The Paris attacks will inevitably raise the question of whether to escalate American and Western military operations in Syria and Iraq. Mr. Obama has authorized airstrikes and sent small teams of Special Operations forces acting as advisers to aid Iraqi military units, Syrian rebels and Kurdish fighters on the ground. But he has strongly resisted a more extensive involvement of American ground troops to avoid repeating what he sees as the mistakes of the Iraq war.

In Mr. Obama’s view, the United States made things worse after Sept. 11 by invading Iraq and toppling Saddam Hussein, stoking a wider anti-American militant movement that ultimately led to the rise of the Islamic State. While critics fault him for pulling American troops out of Iraq in 2011, leaving a vacuum, he has long believed that a greater involvement by the United States would only entangle it in another quagmire without successfully resolving the conflict.

Ms. Townsend and others said that the White House had been too reluctant to acknowledge an “inconvenient truth” — that the Islamic State threat extends beyond the Middle East and could easily lead to a Paris-style attack in the United States.